The present invention relates to an image processing method, an image processing apparatus, and a data recording medium and, more particularly to hierarchical coding and hierarchical decoding wherein an image signal is recorded or transmitted with fewer bits without degrading an image quality, and a recording medium which stores a program for implementing the hierarchical coding or the hierarchical decoding.
In order to perform image processing for each object displayed on a display image, a shape signal indicating a shape of an object as well as a luminance signal and a chrominance signal is necessary as an image signal. In description below, the image signal comprising the shape signal, i.e., shape information of the object, as well as the luminance signal and the chrominance signal is referred to as the xe2x80x9cimage signalxe2x80x9d.
This image signal is suitable for use in multimedia in which image information, audio information and so forth are related to each other simultaneously, since it can be handled for each object. Techniques for coding the image signal is currently standardized by MPEG (Moving Picture Experts Group) 4 as ISO/IEC (International Organization for Standardization/International Electrotechnical Commission Joint Technical Commission) group.
A prior art hierarchical coding of the image signal will now be described.
FIG. 22 shows display images (hereinafter referred to as xe2x80x9cframesxe2x80x9d) corresponding to image signals of different resolutions, respectively. In FIG. 22(a), LF indicates a display image of a low-resolution image signal and in FIG. 22(b), HF indicates a display image of a high-resolution image signal. Lob represents an image of an object of the low-resolution image signal which is displayed on the frame LF. Hob indicates an image of an object of the high-resolution signal which is displayed on the frame HF. In these Figures, an inner portion of each object is represented by dots.
In the prior art image coding (state of the art evaluation model system according to MPEG 4), a rectangular region including an object is set on a frame for each object and the rectangular region is divided into blocks (square blocks MB each comprising (16xc3x9716) pixels in the evaluation model according to MPEG 4). The image signal corresponding to each object is coded for each of the blocks composing the rectangular region.
Hence, in the hierarchical coding according to MPEG4, a low-resolution rectangular region LR is set for an object Lob on a low-resolution frame LF as shown in FIG. 22(c) and a high-resolution rectangular region HR is set for an object Hob on a high-resolution frame HF as shown in FIG. 22(d).
In this hierarchical coding, the rectangular region LR for the low-resolution image signal and the rectangular region HR for the high-resolution image signal are respectively and independently set. As a result, in some cases, although coding itself is performed with ease, spatial positions of respective blocks of each object (positions of respective blocks on the frame) do not match between blocks in the low-resolution rectangular region and blocks in the high-resolution rectangular region and therefore, correspondence does not exist between them.
Hereinafter, this will be described in detail. FIG. 23 is a block diagram showing a prior art hierarchical image coding apparatus.
A prior art image coding apparatus 200a is adapted to receive an input image signal and perform hierarchical coding to the input image signal as a high-resolution image signals HSg. To be specific, the hierarchical image coding apparatus 200a comprises a subsampling unit 2 for subsampling the high-resolution image signal HSg to produce a low-resolution image signal LSg, and a low-resolution coding section 201L for performing coding to the low-resolution image signal LSg to produce a low-resolution coded signal LEg. The apparatus 200a further comprises a decoder 9a for decoding the low-resolution coded signal LEg, an upsampling unit 10a for upsampling an output Ldg of the decoder 9a, and a high-resolution coding section 201H for performing coding to the high-resolution image signal HSg on the basis of an output LAg of the upsampling unit 10a and outputting a high-resolution signal HEg.
The low-resolution coding section 201L includes a region detecting unit 3 for detecting information such as a position or a size of the low-resolution rectangular region LR for each object on the low-resolution frame LF on the basis of the low-resolution image signal LSg and outputting the information as a signal LRg, and a region extracting unit 5 for extracting an image signal LOg (image signal corresponding to a region) of the rectangular region LR from the low-resolution image signal LSg according to the signal LRg. The coding section 201L further includes a blocking unit 6 for dividing the image signal LOg of the rectangular region LR into image signals respectively corresponding to blocks MB each comprising (16xc3x9716) pixels into which the rectangular region is divided, and outputting image signals (blocked image signals) LBg for each block, and an encoder 7 for encoding the blocked image signal LBg and outputting a low-resolution coded signal LEg.
The high-resolution coding section 201H includes a region detecting unit 12 for detecting information such as a position or a size of the rectangular region HR for each object on the high-resolution frame HF on the basis of the high-resolution image signal HSg and outputting the information as a signal HRg and an region extracting unit 14 for extracting an image signal HOg of the rectangular region HR from the high-resolution image signal HSg according to the signal HRg. The coding section 201H further includes a blocking unit 15 for dividing the image signal (image signal corresponding to a region) HOg of the rectangular region HR into image signals respectively corresponding to blocks MB each comprising (16xc3x9716) pixels into which the rectangular region is divided, and outputting image signals (blocked image signals) HBg for each block, and an encoder 16 for encoding the blocked image signal HBg and outputting a high-resolution coded signal HEg.
Subsequently, operation will be described.
When the high-resolution image signal HSg is input to the image coding apparatus 200a as the input image signal, the signal HSg is subjected to subsampling and converted into the low-resolution image signal LSg by the subsampling unit 2.
The region detecting unit 3 of the low-resolution coding section 201L detects a range of the rectangular region LR including the object Lob to be processed on the low-resolution frame FL shown in FIG. 22(c) on the basis of the low-resolution image signal LSg and outputs the information such as a position or a size of the rectangular region as the signal LRg. The region extracting unit 5 extracts the object image signal LOg of the rectangular region LR from the low-resolution image signal LSg according to the signal LRg. The blocking unit 6 divides the object image signal LOg into image signals respectively corresponding to plural blocks MB into which the low-resolution rectangular region LR is divided, and outputs blocked image signals LBg corresponding to respective blocks to the encoder 7. The encoder 7 encodes the blocked image signal LBg, and the low-resolution coded signal LEg is output from the coding section 201L.
The low-resolution coded signal LEg is decoded by the decoder 9a and converted into a low-resolution decoded signal Ldg, which is interpolated and converted into an interpolated decoded signal LAg with the same spatial resolution as the high-resolution image signal and output to the encoder 16 in the high-resolution coding section 201H.
Concurrently with this operation, the high-resolution coding section 201H operates like the low-resolution coding section 201L.
To be specific, the region detecting unit 12 detects a range of the rectangular region HR including an object Hob to be processed on the high-resolution frame HF shown in FIG. 22(d) on the basis of the high-resolution image signals HSg and outputs the information such as a position and a size of the rectangular region HR as the signal HRg. The region extracting unit 14 extracts the object image signal HOg of the rectangular region HR from the high-resolution image signal HSg according to the signal HRg. The blocking unit 15 divides the object image signal HOg into image signals respectively corresponding to plural blocks MB into which the high-resolution rectangular region HR is divided, and outputs blocked image signals HBg to the encoder 16 for each block. The encoder 16 encodes the blocked image signal HBg on the basis of the interpolated decoded signal LAg, and the high-resolution coded signal HEg is output from the coding section 201H.
The low-resolution coded signal LEg thus coded by the hierarchical image coding apparatus 200a is decoded to produce a decoded signal corresponding to the low-resolution image signal LSg on the basis of the signal LRg. Meanwhile, the high-resolution coded signal HEg thus coded by the coding apparatus 200a is decoded to produce a decoded signal corresponding to the high-resolution image signal HSg on the basis of the low-resolution coded signal LEg, the signal LRg, and the signal HRg. In addition, in coding of the high-resolution image signal HSg, by using correlation of pixel values between the image signals LSg and HSg, by referring to the low-resolution image signal LSg, it is possible to perform coding to the high-resolution image signal HSg with fewer bits as compared with a case where the high-resolution image signal HSg is independently coded.
FIG. 24 is a block diagram showing a prior art image decoding apparatus.
A hierarchical image decoding apparatus 200b is adapted to receive the low-resolution coded signal LEg and the high-resolution coded signal HEg which have been coded by the prior art image coding apparatus 200a in FIG. 23 and performs hierarchical decoding to the same.
To be specific, the hierarchical image decoding apparatus 200b comprises a low-resolution decoding section 202L for decoding the low-resolution coded signal LEg to produce a low-resolution reproduced signal LCg, an upsampling unit 10b for interpolating a signal LDg being decoded in the decoding section 202L by upsampling, and a high-resolution decoding section 202H for decoding the high-resolution coded signal HEg to produce a high-resolution reproduced signal HCg on the basis of an output ADg of the upsampling unit 10b. 
The low-resolution decoding section 202L includes a decoder 9 for decoding the low-resolution coded signal LEg to produce a low-resolution decoded signal LDg for each block, an inverse blocking unit 20 for integrating the low-resolution decoded signals LDg to produce a integrated decoded signal LIg corresponding to the rectangular region LR, and a region composition unit 21 for compositing the integrated decoded signal LIg and the other image signals of one frame so that the rectangular region LR is disposed in the position of the low-resolution frame LF as indicated by the signal LRg from the coding apparatus 200a. 
The high-resolution decoding section 202H includes a decoder 30 for decoding the high-resolution coded signal HEg to produce a high-resolution decoded signal HDg for each block on the basis of an output ADg of the upsampling unit 10b, an inverse blocking unit 31 for integrating the high-resolution decoded signals HDg to produce a integrated decoded signal HIg corresponding to the rectangular region HR, and a region composition unit 32 for compositing the integrated decoded signal HIg and the other image signal of one frame so that the rectangular region HR is disposed in the position of the frame HF as indicated by the signal HRg from the coding apparatus 200a. 
Subsequently, operation will be described.
When the low-resolution coded signal LEg and the high-resolution coded image signal HEg are input to the image decoding apparatus 200b, the low-resolution coded signal LEg is decoded to produce the low-resolution decoded signal LDg by the decoder 9 in the low-resolution decoding section 202L. The low-resolution decoded signal LDg is upsampled for interpolation by the upsampling unit 10b and converted into the interpolated decoded signal ADg with a spatial resolution corresponding to the high resolution. The low-resolution decoded signals LDg are integrated by the inverse blocking unit 20 to produce the integrated decoded signal LIg of the rectangular region LR. The integrated decoded signal LIg is composited together with the other image signals of one frame by the region composition unit 21 according to the signal LRg from the coding apparatus 200a and output as the low-resolution reproduced signal LCg. After this composition, an image of the region LR represented by the integrated decoded signal LIg is disposed in the position of the frame LF as indicated by the signal LRg.
Meanwhile, the high-resolution coded signal HEg is decoded by the decoder 30 in the high-resolution decoding section 202H on the basis of the output ADg of the upsampling unit 10b to produce high-resolution decoded signal HDg. The high resolution decoded signals HDg are integrated by the inverse blocking unit 31 to produce the integrated decoded signal HIg corresponding to an image in the rectangular region HR. The integrated decoded signal HIg is composited together with the other image signals of one frame according to the signal HRg from the coding apparatus 200a by the region composition unit 32 and output as the high-resolution reproduced signal HCg. After this composition, an image in the rectangular region HR represented by the integrated decoded signal HIg is disposed on the frame HF as indicated by the signals HRg.
In the hierarchical image decoding apparatus 200b constructed above, after the low-resolution coded signal LEg is decoded and then inversely blocked, the low-resolution decoded signal LIg of the rectangular region LR is composited so that the rectangular region LR is disposed in a predetermined position of the frame LF. Thereby, it is possible to decode the low-resolution coded signal LEg resulting from coding for rectangular region LR including each object in the frame FL.
In addition, after the high-resolution coded signal HEg is decoded by referring to the low-resolution decoded signal LDg, to produce the high-resolution decoded signal HDg, the decoded signals HDg are inversely blocked and then the high-resolution decoded signal HIg of the rectangular region HR is composited so that the rectangular region HR is disposed in a predetermined position in the frame HF. Thereby, it is possible to correctly decode the high-resolution coded signal HEg resulting from hierarchical coding for the rectangular region HR including each object in the frame HF.
However, in the prior art hierarchical image coding apparatus 200a, the range of the rectangular region LR in the low-resolution frame LF and the range of the rectangular region HR in the high-resolution frame HF are respectively and independently detected. For this reason, as shown in FIGS. 22(c) and 22(d), a spatial position of the low-resolution image Lob in each block MB and a spatial position of the high-resolution image Hob in each block MB do not match. Therefore, when coding the high-resolution image signal Hog corresponding to the high resolution rectangular region HR for each block, it is difficult to establish correspondence between high-resolution blocks to be coded and low-resolution blocks, which causes complicated operation of a difference value between the high-resolution image signal and the low-resolution image signal. As a result, when coding the high-resolution blocks, prediction efficiency in hierarchical coding is degraded, and thereby coding efficiency is reduced, as compared with a case where the high-resolution blocks are coded by referring to the low-resolution blocks whose spatial positions perfectly match those of the high-resolution blocks to-be-coded.
The present invention is directed to solving the above problems and, it is an object of the present invention to provide an image processing method and an image processing apparatus which implement hierarchical coding in which coding of a high-resolution image signal with reference to a low-resolution image signal is carried out without degrading coding efficiency when performing hierarchical coding for a rectangular region including an object in a frame, and hierarchical decoding adapted to the hierarchical coding, and a data recording medium which contains a program for implementing the hierarchical coding and the hierarchical decoding by software.
According to a first aspect of the present invention, an image processing method for hierarchically coding an input image signal including shape information of the object, object by object which is included in an image, comprises: producing at least a low-resolution image signal and a high-resolution image signal as hierarchical image signals corresponding to an object, forming plural image spaces of different spatial resolutions, based on the input image signal; extracting a high-resolution region image signal corresponding to a region including the object which is to be coded in a high-resolution image space, from the high-resolution image signal corresponding to the object, dividing the region image signal into image signals respectively corresponding to high-resolution blocks each comprising a predetermined number of pixels, extracting a low-resolution region image signal corresponding to a region including the object which is to be coded in a low-resolution image space, from the low-resolution image signal corresponding to the object, and dividing the region image signal into image signals respectively corresponding to low-resolution blocks each comprising a predetermined number of pixels; and sequentially coding a high-resolution blocked image signal forming a target high-resolution block to be coded, by referring to a low-resolution blocked image signal forming a reference low-resolution block corresponding to the target high-resolution block, wherein a spatial position of the reference low-resolution block in the low-resolution image space corresponds to a spatial position of the target high-resolution block in the high-resolution image space according to a predetermined rule.
In the image processing method constructed above, the high-resolution image signal is coded by referring to the image signal of the low-resolution block located at the spatial position which correlates with the spatial position of the target high-resolution block to-be-coded. As a result, the image signal including shape information can be hierarchically coded without degrading coding efficiency.
According to a second aspect of the present invention, in the image processing method of the first aspect, each pixel in the high-resolution image space has a one-to-one correspondence with each pixel in a resolution-converted image space in which the low-resolution image space has been resolution-converted, the resolution-converted image space having the same spatial resolution as the high-resolution image space.
In the image processing method constructed above, all of plural pixels in the high-resolution block correspond to predetermined pixels in the resolution-converted block in which the low-resolution block has been resolution-converted. As a result, coding efficiency in the hierarchical coding process can be increased.
According to a third aspect of the present invention, in the image processing method of the first aspect, the number of pixels in the reference low-resolution block is equal to the number of pixels in the target high-resolution block.
In the image processing method constructed above, a blocking unit and an encoder are shared by the high-resolution image signal and the low-resolution image signal, whereby a compact circuit structure is realized.
According to a fourth aspect of the present invention, in the image processing method of the first aspect, the spatial position of the reference low-resolution block in the low-resolution image space relatively matches the spatial position of the target high-resolution block in the high-resolution image space.
In the image processing method constructed above, since the spatial position of the target high-resolution block matches the spatial position of the reference low-resolution block, difference between a pixel value of each pixel in the high-resolution block and a pixel value of each pixel in the low-resolution block is not large. As a result, the hierarchical coding process can be performed with higher coding efficiency.
According to a fifth aspect of the present invention, in the image processing method of the first aspect, a coding method for a mode signal indicating a coding mode for identifying the coding process for the target high-resolution block is changed according to a coding mode for identifying a coding process for the reference low-resolution block.
In the image processing method constructed above, a shorter code is assigned to the coding mode for the high-resolution block which matches the coding mode for the low-resolution block. Thereby, it is possible to reduce the number of bits to be coded in the process for coding the mode signal indicating the coding mode for the high-resolution image signal.
According to a sixth aspect of the present invention, in the image processing method of the fifth aspect, the coding mode indicates whether or not a boundary of a shape of an object displayed on an image space is included in the target high-resolution block.
In the image processing method constructed above, when the positional relationship between the high-resolution block and the object matches the positional relationship between the low-resolution block and the object, a shorter code is assigned to the mode signal indicating the coding mode for the high-resolution image signal. Thereby, it is possible to reduce the number of bits to be coded in the process for coding the mode signal.
According to a seventh aspect of the present invention, in the image processing method of the first aspect, a mode signal indicating a coding mode for identifying a coding process for the target high-resolution block is coded according to a coding mode for identifying a coding process for the reference low-resolution block, and the coding mode indicates that the coding process sequentially performed to the image signal of the reference low-resolution block for each pixel is performed in either horizontal or vertical scanning direction.
In the image processing method constructed above, the high-resolution image signal is coded in the scanning direction in which correlation between pixel values thereof is high, and therefore, when there is match between the scanning direction in which correlation between pixel values in the high-resolution image signal is high and the scanning direction in which correlation between pixel values in the low-resolution image signal is high, a shorter code is assigned to the mode signal indicating the coding mode for the high-resolution image signal. Thereby, it is possible to reduce the number of bits to be coded in the process for coding the mode signal.
According to an eighth aspect of the present invention, in the image processing method of the first aspect, a coding method for motion information of the target high-resolution block indicating motion of an object in the high-resolution image space is coded by referring to motion information of a reference low-resolution block indicating motion of an object in the low-resolution image space.
In the image processing method so constructed, since there is high correlation of pixel values between the high-resolution image signal and the low-resolution image signal, when a motion vector of the high-resolution block matches that of the corresponding low-resolution block, a shorter code is assigned to the mode signal indicating the motion vector (coding mode) of the high-resolution image signal. Thereby, it is possible to reduce the number of bits to be coded in the process for coding the motion vector.
According to a ninth aspect of the present invention, in the image processing method of the first aspect, a coding method for motion information of the target high-resolution block indicating motion of an object in the high-resolution image space is coded by referring to motion information of a coded high-resolution block indicating motion of an object in the high-resolution image space and motion information of the reference low-resolution block indicating motion of an object in the low-resolution image space.
In the image processing method constructed above, since the prediction vector is generated from the motion vector of the coded high-resolution block for the target high-resolution block and the motion vector of the low-resolution block for the target high-resolution block, and based on the prediction vector, the motion vector of the target high-resolution block is coded. Since there is correlation of pixel values between frames and there is high correlation of pixel values between the high-resolution image signal and the low-resolution image signal, the error between the motion vector of the target high-resolution block and the prediction motion vector is made smaller. As a result, it is possible to reduce the number of bits to be coded in the process for coding the motion vector of the high-resolution image signal.
According to a tenth aspect of the present invention, an image processing method for decoding at least two blocked and hierarchically coded signals corresponding to an object which are obtained by hierarchically coding an input image signal including shape information of the object, object by object which is included in an image, comprises: decoding a low-resolution coded signal corresponding to the object of the blocked and hierarchically coded signals to produce low-resolution decoded signals of low-resolution blocks each comprising a predetermined number of pixels in a low-resolution image space; integrating the low-resolution decoded signals to produce a low-resolution region image signal corresponding to a region including the object in the low-resolution image space; decoding a high-resolution coded signal corresponding to the object of the blocked and hierarchically coded signals by referring to a reference low-resolution decoded signal to produce high-resolution decoded signals of high-resolution blocks each comprising a predetermined number of pixels in a high-resolution image space; and integrating the high-resolution decoded signals to produce a high resolution region image signal corresponding to a region including the object in the high-resolution image space, wherein a spatial position of the reference low-resolution block in the low-resolution image space relatively corresponds to a spatial position of a target high-resolution block to be decoded in the high-resolution image space according to a predetermined rule.
In the image processing method constructed above, the high-resolution image signal is decoded by referring to the decoded signal of the low-resolution block located at the spatial position in the low-resolution image space which correlates with the spatial position of the target high-resolution block to-be-decoded. As a result, a hierarchical decoding process is carried out in a way adapted to the hierarchical coding process for the image signal including shape information of an object without degrading coding efficiency.
According to an eleventh aspect of the present invention, in the image processing method of the tenth aspect, each pixel in the high-resolution image space has a one-to-one correspondence with each pixel in a resolution-converted image space in which the low-resolution image space has been resolution-converted, the resolution-converted image space having the same spatial resolution as the high-resolution image space.
In the image processing method constructed above, all of plural pixels in the high-resolution block correspond to predetermined pixels in the resolution-converted block in which the low-resolution block has been resolution-converted. Thereby, a hierarchical decoding process is carried out in a way adapted to the high hierarchical coding process with high coding efficiency.
According to a twelfth aspect of the present invention, in the image processing method of the tenth aspect, the number of pixels in the reference low-resolution block is equal to the number of pixels in the target high-resolution block.
In the image processing method constructed above, a decoder and an inverse blocking unit are shared by the high-resolution coded signal and the low-resolution coded signal. As a result, a compact circuit structure is realized.
According to a thirteenth aspect of the present invention, in the image processing method of the tenth aspect, the spatial position of the reference low-resolution block in the low-resolution image space relatively matches the spatial position of the target high-resolution block in the high-resolution image space.
In the image processing method constructed above, a hierarchical decoding process is carried out in a way adapted to the hierarchical coding process with high coding efficiency, in which the spatial position of the target high-resolution block matches that of the reference low-resolution block, difference between a pixel value of each pixel in the high-resolution block and a pixel value of each pixel in the low-resolution block is not large.
According to a fourteenth aspect of the present invention, in the image processing method of the tenth aspect, a decoding method for a coded mode signal indicating a coding mode for identifying a decoding process for the target high-resolution block is changed according to a coding mode for identifying a decoding process for the reference low-resolution block.
In the image processing method constructed above, a hierarchical decoding process is performed in a way adapted to the coding process in which a shorter code is assigned to the mode signal indicating the coding mode for the high-resolution block which matches the coding mode for the low-resolution block, and thereby, it is possible to reduce the number of bits to be coded in the process for coding the mode signal indicating the coding mode for the high-resolution image signal.
According to a fifteenth aspect of the present invention, in the image processing method of the tenth aspect, wherein a coded mode signal indicating a coding mode for identifying a decoding process for the target high-resolution block is decoded according to a coding mode for identifying a decoding process for the reference low-resolution block, and the coding mode indicates whether or not a boundary of a shape of an object displayed on an image space is included in the target high-resolution block.
In the image processing method constructed above, a hierarchical decoding process is carried out in a way adapted to the hierarchical coding process, in which when the positional relationship between the high-resolution block and the object matches the positional relationship between the low-resolution block and the object, a shorter code is assigned to the mode signal indicating the coding mode for the high-resolution image signal, and thereby it is possible to reduce the number of bits to be coded.
According to a sixteenth aspect of the present invention, in the image processing method of the tenth aspect, wherein a coded mode signal indicating a coding mode for identifying a decoding process for the target high-resolution block is decoded according to a coding mode for identifying a decoding process for the reference low-resolution block, and the coding mode indicates that the decoding process sequentially performed to the low-resolution coded signal of the reference low-resolution block for each pixel is performed in either horizontal or vertical scanning direction.
In the image processing method constructed above, a decoding process is carried out in a way adapted to the hierarchical coding process, in which when there is match between the scanning direction in which correlation between pixel values in the high-resolution image signal is high and the scanning direction in which correlation between pixel values in the low-resolution image signal is high, a shorter code is assigned to the mode signal indicating the coding mode for the high-resolution image signal, and thereby it is possible to reduce the number of bits to be coded.
According to a seventeenth aspect of the present invention, in the image processing method of the tenth aspect, motion information of the target high-resolution block indicating motion of an object in the high-resolution image space is decoded according to motion information of the reference low-resolution block indicating motion of an object in the low-resolution image space.
In the image processing method so constructed, a hierarchical decoding process is carried out in a way adapted to the hierarchical coding process, in which, when a motion vector of the high-resolution block matches that of the corresponding low-resolution block, a shorter code is assigned to the mode signal indicating the motion vector (coding mode) of the high-resolution image signal, and thereby it is possible to reduce the number of bits to be coded.
According to an eighteenth aspect of the present invention, in the image processing method of the tenth aspect, motion information of the target high-resolution block indicating motion of an object in the high-resolution image space is decoded according to motion information of a decoded high-resolution block indicating motion of an object in the high-resolution image space and motion information of the reference low-resolution block indicating motion of an object in the low-resolution image space.
In the image processing method constructed above, a hierarchical decoding process is carried out in a way adapted to the hierarchical coding process, in which the error between the motion vector of the target high-resolution block and the prediction motion vector is made smaller, and thereby, it is possible to reduce the number of bits to be coded.
According to a nineteenth aspect of the present invention, an image processing apparatus for hierarchically coding an input image signal including shape information of an object, object by object which is included in an image, comprises: a subsampling means for subsampling the input image signal to produce a low-resolution image signal; a first region extraction means for producing a low-resolution region image signal corresponding to a region including the object which is to be coded in the low-resolution image space, from the low-resolution image signal; a first blocking means for performing a blocking process in such a way that the low-resolution region image signal is divided into signals respectively corresponding to low-resolution blocks each comprising a predetermined number of pixels and outputting low-resolution blocked image signals; a first encoding means for sequentially coding a low-resolution blocked image signal forming a low-resolution block to be coded; a second region extraction means for producing a high-resolution region image signal corresponding to a region including the object which is to be coded in the high-resolution image space, from the high-resolution image signal as the input image signal; a second blocking means for performing a blocking process in such a way that the high-resolution region image signal is divided into signals respectively corresponding to high-resolution blocks each comprising a predetermined number of pixels and outputting high-resolution blocked image signal; and a second encoding means for sequentially coding a high-resolution blocked image signal forming a target high-resolution block to be coded, by referring to a low-resolution blocked image signal forming a reference low-resolution block corresponding to the target high-resolution block, wherein a spatial position of the reference low-resolution block in the low-resolution image space relatively corresponds to a spatial position of the target high-resolution block in the high-resolution image space according to a predetermined rule.
In the image processing apparatus constructed above, the high-resolution image signal is coded by referring to the image signal of the low-resolution block located at the spatial position which correlates with the spatial position of the target high-resolution block to-be-coded. As a result, the image signal including shape information can be hierarchically coded without degrading coding efficiency.
According to a twentieth aspect of the present invention, an image processing apparatus for decoding at least two blocked and hierarchically coded signals corresponding to an object which are obtained by hierarchically coding an input image signal including shape information of the object, object by object which is included in an image, comprises: a first decoding means for decoding a low-resolution coded signal corresponding to an object of the blocked and hierarchically coded signals to produce low-resolution decoded signals of low-resolution blocks each comprising a predetermined number of pixels in a low-resolution image space; a first inverse blocking means for integrating the low-resolution decoded signals of the low-resolution blocks to produce a low-resolution region image signal corresponding to a region including the object in the low-resolution image space; a second decoding means for decoding a high-resolution coded signal corresponding to the object of the blocked and hierarchically coded signals, by referring to a reference low-resolution decoded signal, to produce high-resolution decoded signals of high-resolution blocks each comprising a predetermined number of pixels in a high-resolution image space; and a second inverse blocking means for integrating the high-resolution decoded signals of the high-resolution blocks to produce a high-resolution region image signal corresponding to a region including the object in the high-resolution image space, wherein, a spatial position of the reference low-resolution block in the low-resolution image space, relatively corresponds to a spatial position of the target high-resolution block in the high-resolution image space according to a predetermined rule.
In the image processing apparatus constructed above, the high-resolution image signal is decoded by referring to the decoded image signal of the low-resolution block located at the spatial position in the low-resolution image space, which correlates with the spatial position of the target high-resolution block to be decoded, and thereby the hierarchical decoding process is carried out in a way adapted to the hierarchical coding process for the image signal including shape information of an object with degradation of coding efficiency suppressed.
According to a twenty-first aspect of the present invention, in a data recording medium for storing a program which makes a computer perform a hierarchical image coding process, the program makes the computer perform a hierarchical image coding process according to an image processing method of the first aspect.
In the data recording medium constructed above, use of the computer realizes the hierarchical coding process, in which the high-resolution image signal is coded by referring to the image signal of the low-resolution block located at the spatial position which correlates with the spatial position of the target high-resolution block to-be-coded, and thereby, the image signal including shape information can be hierarchically coded without degrading coding efficiency.
According to a twenty-second aspect of the present invention, a data recording medium for storing a program which makes a computer perform a hierarchical image decoding process, the program makes the computer perform a hierarchical image decoding process according to an image processing method of the tenth aspect.
In the data recording medium constructed above, use of the computer realizes the hierarchical decoding process, in which the high-resolution image signal is decoded by referring to the decoded image signal of the low-resolution block located at the spatial position which correlates with the spatial position of the target high-resolution block to-be-decoded, and thereby, the hierarchical decoding process adapted to the hierarchical coding process for the image signal including shape information of an object with degradation of coding efficiency suppressed.